The present invention relates to a mechanical press, and in particular to such a press having a crankshaft and connection arm assembly which is capable of being inserted into the crown portion of the press in its preassembled form.
A conventional mechanical press comprises a bed which is mounted to a platform or the floor of the shop, a vertically spaced crown portion in which the drive assembly for the slide is contained, and one or more uprights rigidly connecting the bed and crown and maintaining the bed and crown in vertically spaced relationship. The crown contains the drive assembly, which typically comprises a crankshaft having one or more eccentrics thereon and connections connected to the eccentrics of the crankshaft at their upper ends and to the slide at their lower ends, either directly or through a piston arrangement. The slide is mounted within the uprights for vertical reciprocating motion and is adapted to have the upper half of the die set mounted to it with the other half mounted to the bolster, which is connected to the bed.
At one end of the crankshaft, there is usually mounted a flywheel and clutch assembly wherein the flywheel is connected by a belt to the output pulley of the motor so that when the motor is energized, the massive flywheel rotates continuously. When the clutch is energized, the rotary motion of the flywheel is transmitted to the crankshaft which causes the connecting arms to undergo rotary-oscillatory motion that is transmitted to the slide assembly by means of a wrist pin, for example, so that the rotary-oscillatory motion is converted to straight reciprocating motion. The slide is usually mounted in the space defined by the crown, bed and uprights and is guided for rectilinear movement along an axis substantially perpendicular to the plane of the bed.
In the standard press, the crown, uprights and bed are formed as separate units and are connected to each other by means of large tie rods which extend downwardly through openings in the crown, upright and bed and are secured in place by means of large nuts. Due to the very large torque which must be applied to the nuts in order to load the tie rods properly, it is standard practice to heat the tie rods, tighten the nuts and then permit the tie rods to cool thereby contracting in length and becoming loaded to the proper degree. In a press of this type, the crankshaft and connection arms are installed in the crown by inverting the crown, installing the cranks and bearings with the crown inverted, and then assembling the crown containing the crankshaft and connections on top of the uprights and shrinking down the tie rods. This assembly procedure is time consuming and difficult to perform because it necessitates the handling of the large crown casting and a difficult insertion of the components making up the drive assembly. A further disadvantage is the difficulty in servicing the press because to obtain full access to the drive assembly, it is necessary to heat up the tie rods, remove the top nuts, and remove and invert the crown.